This invention relates to insulated gate bipolar transistors (IGBTs), and more specifically relates to a novel integral gate resistor for such devices to improve their operation when connected in parallel.
IGBTs are well known MOS gate controlled bipolar transistors. Such devices are described in application Ser. No. 08/041,136, filed Mar. 30, 1993, now refiled as continuation application Ser. No. 08/316,112, filed Sep. 30, 1994, entitled POWER TRANSISTOR DEVICE HAVING ULTRA DEEP INCREASED CONCENTRATION REGION, and is assigned to the assignee of the present invention. The use of two or more IGBT devices in parallel circuit connection is also known, and is described in copending application Ser. No. 08/122,052, filed Sep. 15, 1993, in the name of Courtney Furnival, which is also assigned to the assignee of the present invention.
When IGBTs are connected in parallel, for example, when connecting plural IGBTs on a common heat sink to increase the current capacity of an assemblage of IGBTs, it is known that the load current may tend to oscillate between the parallel IGBTs. This effect is reduced by connecting small resistors in the gate circuits of the IGBTs. The desired gate resistance value will vary from about 5 ohms to 50 ohms, depending on the number of die which are connected in parallel. The added gate resistors require an added component which takes up added space in an assembly, for example, the IGBT module of application Ser. No. 08/122,052, referred to above, and requires additional assembly steps.